Well completion method



Jlme 3, 1958 T. o. ALLEN `ET AL 2,837,154

WELL COMPLETION METHOD Filed OCT.. 12, 1955 FIG. /A FIG. /B FIG. /c FIG./D

INVENTORS. moms @.ALLEN, E BYALaE/rr n'. coz/ren .13.,

Arro N r.-

United States Patent f() 2,837,164 WELL COMPLETION METHOD ApplicationOctober l2, 1955, Serial No. 540,068 1 Claim. (Cl. 166-22) The presentinvention is directed to a well completion method. More particularly,the present invention is concerned with forming clean perforations in awell bore.` In this more specific aspects, the invention has to do withcompleting a well in which a well casing `is perforated.

The present invention may begbriey described as a method for formingclean` perforations and completing `a well in a wellbore penetrating asubsurface interval. The invention includes arranging in the `well boreadjacent the subsurface interval a suspension comprising at least twonely divided solid materials in a liquid vehicle. The solid materials inthe suspension are characterized by being chemically interacting andbeing separable from` the` liquid vehicle by ltration. The well bore isthen perforated in the suspension byV operating a perforator, such` asfiring a gun perforator inserted therein, whereby filter plugs areformed in resulting perforations which temporarily plug the perforationsuntil chemical interaction between the solids in the 'lter plug causesvdestruction of the lterplug.

u It is contemplated in the present invention that the well bore mayhave a casing arranged therein which will be perforated by theperforator, such as a gun perforator,

i i which may be of ashape charge or bullet gun type. lt is also withinthe purview of the present invention to complete a well in which awellboreor a well casing is perforated by firing a gun perforator in a firstsuspension terials in the two suspensions being capable of interactingand causing destruction of the plug. After the plug has beendestroyed ineither of the two modes described, the well may then be brought` invandcompleted to produce earth fluids, such as oil and/or gas, water, `andthe like therefrom.

The present invention broadly contemplates replacing drilling mud in awell with a suspension of linely divided solids which forms a ilter plugin the perforations and which is capable of reacting withanother solidto destroy the ilter plug. The suspension or uid and the plugs formedtherefrom may have the following characteristicsi "(l) The uid containsmaterials which would enter tively low level.

vri ce to intimate contact with the carrying agent of fluid placed inthe bottom of the hole at the time of perforating, or the plug` may bepartially destroyed by lluids in the formation following theperforating.

(5) This plug may not be completely destructible, but it is possiblethat only a portion of the plug will be destroyed, thus allowing theremainder of the plug to be cleaned out by uid ow from the reservoir.

(6) Rather than being destroyed, the plug, after'it is placed in theperforation, may shrink with time so that it becomes smaller than theperforation and can be easily flowed out of the perforation. 4

As an illustration of the type of suspension which may be used in whicha filter plug is formed may be mentioned a suspension of calciumhydroxide and ammonium chloride in stoichiometrical proportions as shownin the following equation:

With these two materials, the filter cake plug in perforations wouldbreak down into calcium chloride, ammonia, and water. By controlling theparticle size, the self-destroying reaction could be a timed device toallow normal well completion operations to be completed prior to thedestruction of the plug, since it is desirable thatvthe plug remainessentially intact or be reformed rather rapidly to limit iluid lossinto the formation. In addition, it is of great importance that the plugbe selfdestructible to the extent that it can be pushed from theperforation byfluids from the formation when the differential pressureis from theformation into the well bore. ln order to get the desiredweight characteristics for the perforating fluid which is located belowthel column of drilling fluid, it may be desirable to mix a certainpercentage of barytes or other high density solids with `theself-destructible materials which would form the perforation plug. In`this invention, as previously stated, the high density weightingmaterial would not be destroyed and tend to remain in the perforationwhile the selfdestructible portion of the plug isv being converted to aiiuid or a gas. However, if at least 25 percent of the t plug in theperforation is converted to a gas or liquid, the

structure of the plug would be appreciably weakened by the destructionof a portion of the solid plug, thereby allowing the plug to be brokendown and easily removed.

p In order to obtain desired weight, it may also be necesthe types ofsubstances which may be used in stoichio- (2) `Thisplug isself-destructible and either completely or partially reverts to a duidor gas with time, temperai i i `trolled by particle size.

y(4) This self-destructible plug may be a single solid which isdestroyed after a definite period of time due metrical proportionstopreact together to form non-plugging lter plugs are solid acids andbases, and solid oxidizing and reducing substances wherein the rate ofselfdestruction depends on the particular substances used and the amountof water added, if any is employed. As a general statement, it may besaid that the solids may be capable of reacting together to destroy thelter Vplug within a time no greater than 24 hours. The time in which thefilter plug will be destroyed by itself may vary depending on thetemperature in the well bore which may rang anywhere from about 80 up toabout 300 F.

As pairs of solid inorganic acids and solid bases which i may be usedmay be mentioned the following:

Boric acid and sodium hydroxide, silicio acid and sodium hydroxide,arsenic trioxide (with 0.5 equivalent of water) and sodium hydroxide,sulfamic acid and sodium hydroxide and sulfamic acid and sodiumcarbonate.

As typical examples of solid organic acids with solid bases which may beused may be mentioned the following: Oxalic acid and, sodium carbonate,voxalic -acid and calcium carbonate, adipic lacid and sodium hydroxide,adipic acid and sodium bicarbonate, adipic acid and ammoniumbicarbonate, adipic acid and sodium carbonate, fumarie acid and sodiumcarbonate, fumarie acid and sodium hydroxide, maleic anhydride andsodium hydroxide, maleic anyhdride and calcium carbonate, citric acidand sodium hydroxide, citric acid and sodium carbonate, tartaric acidand sodium hydroxide, benzoic acid and sodium hydroxide, benzoic acidand ammonium bicarbonate, benzoic acid and calcium carbonate, salicylicacid and sodium hydroxide, phthalic anhydride and sodium hydroxide,phthalic anhydride and calcium carbonate.

There are many solid mineral acid salts of weak bases which arereactable with inorganic bases to destroy a filter plug among which maybe mentioned:

Ammonium sulfate and sodium hydroxide, ammonium mono H phosphate andsodiu hydroxide, ammonium thiocyanate and sodium hydroxide, ammoniumthiocyanate and calcium hydroxide, ammonium oxalate and sodiumhydroxide, ammonium citrate and sodium hydroxide, ammonium citrate andstrontium hydroxide, ammonium chromate and sodium hydroxide, ammoniumdichromate and sodium hydroxide, ammonium iodide and calcium hydroxide,ammonium bromide and calcium hydroxide, ammonium bifluoride and sodiumhydroxide, ammonium carbonate and sodium hydroxide, ammonium bicarbonateand sodium hydroxide, ammonium alum and sodium hydroxide, ammonium alumand potassium hydroxide, ammonium acetate and sodium hydroxide, ammoniumacetate and calcium hydroxide, ammonium nitrate and magnesium hydroxide,hydrazine sulfate and magnesium hydroxide, hydroxylamine sulfate andmagnesium hydroxide, hydrazine hydrochloride and sodium hydroxide,guanidine hydrochloride and sodium hydroxide, ethanolamine hydrochlorideand sodium hydroxide, ethylene diamine hydrochloride and sodiumhydroxide, ethylene diamine hydrochloride and magnesium hydroxide,ethylene diamine hydrochloride and barium hydroxide, ethylene diami-nehydrochloride and zinc oxide, butyl amine hydrochloride and sodiumhydroxide, octyl amine hydrochloride and magnesium hydroxide, N, Ndioctyl amine hydrochloride and sodium hydroxide, aniline hydrochlorideand sodium hydroxide, aniline hydrochloride and magnesium hydroxide,aniline sulfate and magnesium hydroxide, aniline sulfate and Zinc oxide,pyridine hydrochloride and sodium hydroxide, quinoline hydrochloride andsodium hydroxide, quinoline hydrochloride and magnesium hydroxide.

Of particular interest and usefulness in the present invention are solidammonium salts reactable with solid bases; typical examples of which maybe mentioned:

Ammonium chloride and magnesium hydroxide, ammonium chloride and sodiumhydroxide, ammonium chloride and potassium hydroxide, ammonium chlorideand lithium hydroxide, ammonium chloride and zinc oxide, ammoniumchloride and tin oxide, ammonium chloride and aluminum hydroxide,ammonium chloride and aluminum oxide, ammonium chloride and berylliumoxide, ammonium chloride and antimony trioxide, ammonium chloride andnickelous hydroxide, ammonium chloride and calcium sulfide, ammoniumchloride and barium sulfide, ammonium chloride and calcium lactate,ammonium chloride and ferrous lactate, ammonium chloride and magnesiumlactate, ammonium chloride and manganese lactate, ammonium nitrate andcalcium sulde, ammonium nitrate and Zinc oxide, ammonium nitrate andaluminum hydroxide, ammonium nitrate and aluminum oxide, ammoniumnitrate and beryllium oxide, ammonium nitrate and a-ntimony trioxide,ammonium nitrate and nickelous hydroxide, ammonium nitrate and ferrouslactate, ammonium nitrate and calcium hydroxide, ammonium nitrate andmagnesium hydroxide, ammonium nitrate and magnesium lactate, andammonium nitrate and manganese lactate.

It is possible to use solid reducing agents with solid oxidizing agents,as illustrated by the following reactants, to form self-destructibleplugs on perforating a subsurface interval in a suspension thereof:

Hydroxylamine hydrochloride and ammonium nitrate, hydroxyl amine andsodium nitrate, hydroxyl amine hydrochloride and ammonium persulfate,hydrazine sulfate and ammonium nitrate, hydrazine sulfate and sodiumnitrate, hydrazine sulfate and potassium nitrate, sulfamic acid andammonium nitrate, paraform and ammonium nitrate, paraform and sodiumnitrate, paraform and potassium nitrate, paraform and sodium nitrite,paraform and sodium chlorate, paraform and potassium chlorate, paraformand sodium bromate, paraform and potassium iodide, paraform andpotassium perchlorate, paraform and ammonium chromate, paraform andammonium persulfate, paraform and hydroxylamine hydrochloride, trioxaneand ammonium nitrate, trioxane and sodium chlorate, hydroquinone andammonium nitrate, hydroquinone and sodium nitrate, hydroquinone andsodium chlorate, hydroquinone and sodium bromate, hydroquinone andammonium chromate, hydroquinone and ammonium dichromate, hydroquinoneand chromium trioxide, hydroquinone and ammonium persulfate,hydroquinone and sodium borate, catechol and ammonium nitrate, catecholand sodium chlorate, o-phenylene diamine and ammonium nitrate,o-phenylene diamine and sodium chlorate, ophenylene diamine and chromiumtrioxide, oxalic acid and ammonium nitrate, oxalic acid and sodiumnitrate, oxalic acid and sodium chlorate, oxalic acid and hydroxylaminehydrochloride, paraform and ammonium nitrate, paraform and sodiumnitrate, paraform and potassium nitrate, paraform and sodium nitrite,hydroxylamine hydrochloride and ammonium nitrate, hydroxylaminehydrochloride and sodium nitrate, hydrazine sulfate and ammoniumnitrate, hydrazine sulfate and sodium nitrate, hydrazine sulfate andpotassium nitrate, catechol and ammonium nitrate, oxalic acid and sodiumnitrate, sugar and ammonium nitrate, sugar and sodium nitrate, paraformand sodium chlorate, paraform and potassium chlorate, paraforrn andsodium bromate, paraform and potassium iodide, paraform and potassiumperchlorate, hydroquinone and sodium chlorate, hydroquinone and sodiumbromate, catechol and sodium chlorate, sugar and sodium chlorate,paraform and ammonium chromate, hydroquinone and ammonium chromate,hydroquinone and ammonium dichromate, hydroquinone and chromiumtrioxide, o-phenylene diamine and chromium trioxide,`cellulose andammonium persulfate, paraforrn and ammonium persulfate, hydroxylaminehydrochloride and ammonium persulfate, cellulose and ammoniumpersulfate, cellulose and hydroxylamine,hydrochloride, cellulose andpicric acid, cellulose and zinc chloride, cellulose and aluminumchloride, Wood flour and picric acid, Wood flour and zinc chloride, Woodflour and sodium peroxide.

lt may be desirable to form the two solids in an emulsion or suspensionby using a hydrocarbon vehicle as the suspending agent. As examples ofthe hydrocarbon vehicles which may be employed may bementionedhydrocarbons boiling in the range from about 200 to about 750F. and particularly petroleum naphthas and fractions in this boilingrange. Kerosene and gas oil fractions may also be suitable. Under someconditions, it may be desirable to use lubricating oil fractions as thesuspension material. In fact by virtue of the viscosity of the highboiling fractions, lubricating oil may be preferred under someinstances. When other fractions are used, it may be desirable to addWeighting agents to provide the necessary Weight and/or viscosity to thefluids. Suitable thickening agents, such as metallic soaps of the fattyacids as exemplified by stearic, oleic, linoleic, linolenic, recinoleic,and the like acids, as well as fulfonic acids, may be used.

The proportions of the solids, for example, ammonium chloride andcalcium hydroxide may range from .about to about 10% by volume of water.

` about 7% to about 22% by weight of calcium hydroxide.

In forming an emulsion, it may be desirable to form a Water-in-oilemulsion which may contain up to about 5% materials or thickening agentsandthe like may be used if desired.

By varying the amount of water in the suspension, the

Suitable stabilizing time for self-destruction of the filter plug may becon- 1 trolled.

It is desirable to control the particle sizes of the solids ,i in thesuspension and it is desirable that the solids may range from about a 2mesh to about a 200 mesh with the particle sizes being proportioned inthe intermediate ranges to provide the proper bridgingcharacteristics tothe particles in the suspension from which the filter plug is formed onperforating the casing.

In the present invention the perforation of the well bore or casing andformation, for example, when a gun `perforator is employed, results in afilter plug being formed in the perforations due to the solid materialsbeing carried into the perforations and the loss of water therefrorn.This filter plug which, if not removed, would obviate the benefits ofperforating the drill bore and/or casing since a solid plug would beformed which would obstruct passage of desirable fluid into the wellbore. ByV

providing a suspension which is self-destructible, the filter plug isdestroyed at least partially which allows the well to be readilyproducible by flowing or swabbing as may `another solid andan aqueous oroily vehicle such as ammonium `chloride in water and/ or an emulsionformed from hydrocarbon and water.

In these instances, the second suspension or uid would contact `thefilter plug `for a period of time ranging from about 15 minutes to tabout 24 hours to cause destruction of the lter plug.

It will be seen from the foregoing description that the presentinvention is applicable to many variations.

The invention will be further described by reference to the drawing inwhich Figs. 1A to 1D represent a stepwise illustration of a preferredmode. Referring now to the drawing, in which identical numeralswill beemployed to designate identical parts, numeral 11 designates a well boredrilled from the earths surface, not shown, to penetrate a plurality ofsubsurface earth formations, strata, intervals or zones A, B, and C. lnthis particular instance, intervals or zones A and Cmay be considered tobe productive of hydrocarbons, such as oil and/or gas, and zone B isnon-productive. Arranged in the well bore 11 is a casing 12 which iscemented in place with cement 13. Suspended from the well head of thewell by means, not shown, is a tubing string 14 which may be permanentlyset in the well with its lower open end 15 above the intervals A, B, andC or whichmay `be manipulatable in the well. When the tubing 14 ispermanently set in the Well,

. it may be desirable to employ a tubular extension member i [designatedgenerally by the numeral 16 landed in the lower end of the tubing 14 andsupported, anchored or suspended therein in a landing nipple 17 andsealed by a sealing means 13. The extension member 16 is provided with afishing head or neck 19 for removal of the extension member 16 by meansof a wire line not shown.

` divided solids as illustrated supra. The drilling mud may have beenreplaced or circulated out by lowering the tubing 14 as indicated by thedotted lines, if the tubing is not permanently set in the well, or byemploying the tubular extension member 16 to reverse out at least partof the drilling mud or displace same with the suspension 21 which mayhave a weight and/or viscosity sufiicient to displace the drilling mudat least in part.

in Fig. 1C a gun perforator, such as 22, provided with a plurality ofbullets or shape charges 23, is lowered through the tubing 14 on a wireline 22 until it is positioned adjacent the interval A and then fired toperforate the casing 12, cement 13, and interval A to form perforations24 which, immediately on firing of the gun perforator, become pluggedwith a self-destructible filter plugZS which will destroy itself byinteraction of the chamicals from the suspension after a period of timeranging from about l5 minutes up to about 24 hours. After this time haselapsed, the filter plug 25 will destroy itself at least in part and maybe swabbed or flowed from the perforations 24 as shown in Fig. 1D andthe well brought into production to produce the desirable earth fluids,such as oil and/or gas, water, and the like.

In accordance with the present invention, as stated hereinbefore,instead of firing the gun perforator 22 in a suspension comprising twofinely divided solids, as shown in Fig. 1C, a suspension 'comprisingonly one of the finely divided solids may be used and the gun perforator:tired in said suspension to form a filter plug, such as 25, andthereafter the rst suspension may be replaced by a second suspension orfluid which may remain in contact with the filter plug for a time withinthe range from 15 minutes to 24 hours to cause destruction of the filterplug and allow the well to be brought into production, as shown in Fig.1D.

The present invention is of considerable advantage and utility in thatheretofore unless a well was perforated in a non-plugging uid as set outin U. S. Patent 2,693,856, issued November 9, 1954, to Thomas O. Allenthe perforaktions so formed would become plugged with drilling mud torender the operation sometimes entirely useless. 1n accordance with thepresent invention, the perforation is conducted in a suspension or uidwhich will form a filter plug but which will destroy itself within aperiod of time within the range given.

The nature and objects of the present invention having been completelydescribed and illustrated, what we wish to claim as new and `useful andto secure by Letters Patent is:

A method for forming clean perforations in a well borepenetrating asubsurface earth interval having a casing arranged therein whichcomprises arranging in said well casing adjacent said interval asuspension comprising a mixture of at least two finely divided solidmaterials in a liquid vehicle, said solid materials being capable ofchemically interacting and of being separable from the liquid vehicle byfiltration, and then gun perforating said casing in said suspensionwhereby a filter plug is formed in the resulting perforations whichtemporarily plug said perforations until chemical interaction betweenthe solids in the filter plug causes destruction thereof, said mixturebeing selected from the group consisting of mixtures of solid inorganicacids with solid inorganic bases; solid organic acids with solidinorganic bases; solid mineral acid salts of weak bases with inorganicbases; solid ammonium salts with solid inorganic bases; and solidreducing agents with solid oxidizing agents.

References Cited in the flle of this patent UNITED STATES PATENTS2,193,775 Stratford Mar. 12, 1940 2,207,184 White July 9, 1940 2,591,807Greene Apr. 8, 1952 2,693,856 Allen Nov. 9, 1954 2,699,213 Cardwell etal Ian. 11, 1955 2,718,264 Allen et al. Sept. 20, 1955

